That's not the point - the idea of Free Speech is to protect people from having their voices silenced simply on the grounds that it offends or bothers another person/group. The WBC is the essence of hate and bigotry, but their right to be hateful bigots is the greatest thing about America and Free Speech.
You grossly misstate the point in your OP, and now here again. No one is denying WBC their "freedom of speech". They are denying their ability to conduct it on private property, and/or on state property where it is seen as disruptive to the stated public use of that property. You have a right to visit a cemetery, for whatever reason, so long as you conduct yourself there in a manner that is OK with the owners of the cemetery. You can visit such as the US Capital, and the WH, so long as you do not interfere with the conduct of business there. You can't go into a Congressional hearing and start protesting and be expected to be allowed to stay. None of that is a violation of "free speech".